Individuals with MVP are at higher risk of bacterial infection of the heart, called infective endocarditis. This risk is approximately three- to eightfold the risk of infective endocarditis in the general population. Until 2007, the American Heart Association recommended prescribing antibiotics before invasive procedures, including those in dental surgery. Thereafter, they concluded that "prophylaxis for dental procedures should be recommended only for patients with underlying cardiac conditions associated with the highest risk of adverse outcome from infective endocarditis."

Many organisms responsible for endocarditis are slow-growing and may not be easily identified on routine blood cultures (these fastidious organisms require special culture media to grow). These include the HACEK organisms, which are part of the normal oropharyngeal flora and are responsible for perhaps 5 to 10% of infective endocarditis affecting native valves. It is important when considering endocarditis to keep these organisms in mind.

MVP may occur with greater frequency in individuals with Ehlers-Danlos syndrome, Marfan syndrome or polycystic kidney disease. Other risk factors include Graves disease and chest wall deformities such as pectus excavatum. For unknown reasons, MVP patients tend to have a low body mass index (BMI) and are typically leaner than individuals without MVP.

Rheumatic fever is common worldwide and responsible for many cases of damaged heart valves. Chronic rheumatic heart disease is characterized by repeated inflammation with fibrinous resolution. The cardinal anatomic changes of the valve include leaflet thickening, commissural fusion, and shortening and thickening of the tendinous cords. The recurrence of rheumatic fever is relatively common in the absence of maintenance of low dose antibiotics, especially during the first three to five years after the first episode. Heart complications may be long-term and severe, particularly if valves are involved. Rheumatic fever, since the advent of routine penicillin administration for Strep throat, has become less common in developed countries. In the older generation and in much of the less-developed world, valvular disease (including mitral valve prolapse, reinfection in the form of valvular endocarditis, and valve rupture) from undertreated rheumatic fever continues to be a problem.

In an Indian hospital between 2004 and 2005, 4 of 24 endocarditis patients failed to demonstrate classic vegetations. All had rheumatic heart disease (RHD) and presented with prolonged fever. All had severe eccentric mitral regurgitation (MR). (One had severe aortic regurgitation (AR) also.) One had flail posterior mitral leaflet (PML).

Quadricuspid aortic valves are very rare cardiac valvular anomalies with a prevalence of 0.013% to 0.043% of cardiac cases and a prevalence of 1 in 6000 patients that undertake aortic valve surgery. There is a slight male predominance in all of the cases, and the mean age is 50.7.

In Heyde's syndrome, aortic stenosis is associated with gastrointestinal bleeding due to angiodysplasia of the colon. Recent research has shown that the stenosis causes a form of von Willebrand disease by breaking down its associated coagulation factor (factor VIII-associated antigen, also called von Willebrand factor), due to increased turbulence around the stenotic valve.

Bicuspid aortic valves are the most common cardiac valvular anomaly, occurring in 1–2% of the general population. It is twice as common in males as in females.

Bicuspid aortic valve is a heritable condition, with a demonstrated association with mutations in the NOTCH1 gene. Its heritability (formula_1) is as high as 89%. Both familial clustering and isolated valve defects have been documented. The incidence of bicuspid aortic valve can be as high as 10% in families affected with the valve problem..Recent studies suggest that BAV is an autosomal dominant condition with incomplete penetrance. Other congenital heart defects are associated with bicuspid aortic valve at various frequencies, including coarctation of the aorta.

Almost all cases of mitral stenosis are due to disease in the heart secondary to rheumatic fever and the consequent rheumatic heart disease. Uncommon causes of mitral stenosis are calcification of the mitral valve leaflets, and as a form of congenital heart disease. However, there are primary causes of mitral stenosis that emanate from a cleft mitral valve. It is the most common valvular heart disease in pregnancy.

Other causes include infective endocarditis where the vegetations may favor increase risk of stenosis. Other rare causes include mitral annular calcification, endomyocardial fibroelastosis, malignant carcinoid syndrome, systemic lupus erythematosus, whipple disease, fabry disease, and rheumatoid arthritis. hurler' disease, hunter's disease, amyloidosis.

The natural history of mitral stenosis secondary to rheumatic fever (the most common cause) is an asymptomatic latent phase following the initial episode of rheumatic fever. This latent period lasts an average of 16.3 ± 5.2 years. Once symptoms of mitral stenosis begin to develop, progression to severe disability takes 9.2 ± 4.3 years.

In individuals having been offered mitral valve surgery but refused, "survival" with medical therapy alone was 44 ± 6% at 5 years, and 32 ± 8% at 10 years after they were offered correction.

Inflammation of the heart valves due to any cause is called valvular endocarditis; this is usually due to bacterial infection but may also be due to cancer (marantic endocarditis), certain autoimmune conditions (Libman-Sacks endocarditis, seen in systemic lupus erythematosus) and hypereosinophilic syndrome (Loeffler endocarditis). Certain medications have been associated with valvular heart disease, most prominently ergotamine derivatives pergolide and cabergoline.

Valvular heart disease resulting from rheumatic fever is referred to as "rheumatic heart disease". Damage to the heart valves follows infection with beta-hemolytic bacteria, such as typically of the respiratory tract. Pathogenesis is dependent on cross reaction of M proteins produced by bacteria with the myocardium. This results in generalized inflammation in the heart, this manifests in the mitral valve as vegetations, and thickening or fusion of the leaflets, leading to a severely compromised buttonhole valve.

Rheumatic heart disease typically only involves the mitral valve (70% of cases), though in some cases the aortic and mitral valves are both involved (25%). Involvement of other heart valves without damage to the mitral are exceedingly rare.

While developed countries once had a significant burden of rheumatic fever and rheumatic heart disease, medical advances and improved social conditions have dramatically reduced their incidence. Many developing countries, as well as indigenous populations within developed countries, still carry a significant burden of rheumatic fever and rheumatic heart disease and there has been a resurgence in efforts to eradicate the diseases in these populations.

The risk of death in individuals with aortic insufficiency, dilated ventricle, normal ejection fraction who are asymptomatic is about 0.2 percent per year. Risk increases if the ejection fraction decreases or if the individual develops symptoms.

Individuals with chronic (severe) aortic regurgitation follow a course that once symptoms appear, surgical intervention is needed. AI is fatal in 10 to 20% of individuals who do not undergo surgery for this condition. Left ventricle dysfunction determines to an extent the outlook for severity of aortic regurgitation cases.

Notwithstanding the foregoing, the American Heart Association has recently changed its recommendations regarding antibiotic prophylaxis for endocarditis. Specifically, as of 2007, it is recommended that such prophylaxis should be limited only to those with prosthetic heart valves, those with previous episode(s) of endocarditis, and those with certain types of congenital heart disease.

Since the stenosed aortic valve may limit the heart's output, people with aortic stenosis are at risk of syncope and dangerously low blood pressure should they use any of a number of medications for cardiovascular diseases that often coexist with aortic stenosis. Examples include nitroglycerin, nitrates, ACE inhibitors, terazosin (Hytrin), and hydralazine. Note that all of these substances lead to peripheral vasodilation. Under normal circumstances, in the absence of aortic stenosis, the heart is able to increase its output and thereby offset the effect of the dilated blood vessels. In some cases of aortic stenosis, however, due to the obstruction of blood flow out of the heart caused by the stenosed aortic valve, cardiac output cannot be increased. Low blood pressure or syncope may ensue.

Heart valve dysplasia is an error in the development of any of the heart valves, and a common cause of congenital heart defects in humans as well as animals; tetralogy of Fallot is a congenital heart defect with four abnormalities, one of which is stenosis of the pulmonary valve. Ebstein's anomaly is an abnormality of the tricuspid valve.

Some recent research has suggested that a proportion of cases of migraine may be caused by PFO. While the exact mechanism remains unclear, closure of a PFO can reduce symptoms in certain cases. This remains controversial; 20% of the general population has a PFO, which for the most part, is asymptomatic. About 20% of the female population has migraines, and the placebo effect in migraine typically averages around 40%. The high frequency of these facts finding statistically significant relationships between PFO and migraine difficult (i.e., the relationship may just be chance or coincidence). In a large randomized controlled trial, the higher prevalence of PFO in migraine patients was confirmed, but migraine headache cessation was not more prevalent in the group of migraine patients who underwent closure of their PFOs.

Bicuspid aortic valve abnormality is seen in 1 to 2 percent of all live births. It is associated with a number of mutations affecting Notch signalling pathway.

The mitral valve apparatus comprises two valve leaflets, the mitral valve annulus, which forms a ring around the valve leaflets, and the papillary muscles, which tether the valve leaflets to the left ventricle and prevent them from prolapsing into the left atrium. The "chordae tendineae" are also present and connect the valve leaflets to the papillary muscles. Dysfunction of any of these portions of the mitral valve apparatus can cause regurgitation.

The most common cause of MI in developing countries is mitral valve prolapse (MVP). and is the most common cause of primary mitral regurgitation in the United States, causing about 50% of cases. Myxomatous degeneration of the mitral valve is more common in women as well as with advancing age, which causes a stretching of the leaflets of the valve and the chordae tendineae. Such elongation prevents the valve leaflets from fully coming together when the valve closes, causing the valve leaflets to prolapse into the left atrium, thereby causing MI.

Ischemic heart disease causes MI by the combination of ischemic dysfunction of the papillary muscles, and the dilatation of the left ventricle. This can lead to the subsequent displacement of the papillary muscles and the dilatation of the mitral valve annulus.

Rheumatic fever and Marfan's syndrome are other typical causes. MI and mitral valve prolapse are also common in Ehlers Danlos Syndrome.

Secondary mitral insufficiency is due to the dilatation of the left ventricle that causes stretching of the mitral valve annulus and displacement of the papillary muscles. This dilatation of the left ventricle can be due to any cause of dilated cardiomyopathy including aortic insufficiency, nonischemic dilated cardiomyopathy, and Noncompaction cardiomyopathy. Because the papillary muscles, chordae, and valve leaflets are usually normal in such conditions, it is also called functional mitral insufficiency.

Acute MI is most often caused by endocarditis, mainly "S. aureus". Rupture or dysfunction of the papillary muscle are also common causes in acute cases, dysfunction, which can include mitral valve prolapse.

A patent foramen ovale (PFO) is a small channel that has some hemodynamic consequence; it is a remnant of the fetal foramen ovale, which normally closes at birth. In medical use, the term "patent" means open or unobstructed. In about 25% of people, the foramen ovale fails to close properly, leaving them with a PFO or at least with what some physicians classify as a "pro-PFO", which is a PFO that is normally closed, but can open under increased blood pressure. On echocardiography, shunting of blood may not be noted except when the patient coughs.

Clinically, PFO is linked to stroke, sleep apnea, migraine with aura, and decompression sickness. No cause is established for a foramen ovale to remain open instead of closing naturally, but heredity and genetics may play a role.

The mechanism by which a PFO may play a role in stroke is called paradoxical embolism. In the case of PFO, a blood clot from the venous circulatory system is able to pass from the right atrium directly into the left atrium via the PFO, rather than being filtered by the lungs, and thereupon into systemic circulation toward the brain. PFO is common in patients with atrial septal aneurysms (ASA) which are also linked to cryptogenic (i.e. of unknown cause) strokes.

PFO is more prevalent in patients with cryptogenic stroke than in patients with a stroke of known cause. While PFO is present in only 25% in the general population, the probability of someone having a PFO increases to about 40 to 50% in patients who have had a cryptogenic stroke. Statistically speaking, this is particularly true for patients who have a stroke before the age of 55.

PFO is not treated in the absence of other symptoms, and no consensus exists on treatment of PFO even in the presence of transient ischemic attack or stroke. Moreover, no "gold standard" treatment option is known. However, treatments for PFO include surgical closure and percutaneous device closure, as well as medical therapies such as anticoagulant therapy, and antiplatelet agents.

Research studies of the efficacy of surgical closure treatments versus medical therapies of PFOs in preventing the recurrence of strokes have been conducted; the results are mixed, although “as-treated” and “per-protocol” analyses were positive for closure devices.

PFO closure devices may be implanted via catheter-based procedures, and using a variety of closure devices.

Debate exists within the neurology and cardiology communities about the role of a PFO in cryptogenic neurologic events such as strokes and transient ischemia attacks without any other potential cause. Some data suggest that PFOs may be involved in the pathogenesis of some migraine headaches. Several clinical trials are currently underway to investigate the role of PFO in these clinical situations.

In terms of the cause of aortic insufficiency, is often due to the aortic root dilation ("annuloaortic ectasia"), which is idiopathic in over 80% of cases, but otherwise may result from aging, syphilitic aortitis, osteogenesis imperfecta, aortic dissection, Behçet's disease, reactive arthritis and systemic hypertension. Aortic root dilation is the most common cause of aortic insufficiency in developed countries. Additionally, aortic insufficiency has been linked to the use of some medications, specifically medications containing fenfluramine or dexfenfluramine isomers and dopamine agonists. Other potential causes that affect the valve directly include Marfan syndrome, Ehlers–Danlos syndrome, ankylosing spondylitis, and systemic lupus erythematosus. In acute cases of aortic insufficiency, the main causes are infective endocarditis, aortic dissection or trauma.

The most common complications of QAV are aortic regurgitations. This is caused by the inadequate closing of the four cusps during systole. The fourth dysplastic cusp is incapable of fully closing the aortic annulus, which causes a backflow of blood through the aortic valve. Using transthoracic echocardiograms, 3-D TEE and ECG traces, it is also possible to find left ventricular hypertrophy, bundle branch blocks, and abnormal displacement of the ostium in the right coronary artery in association with QAV. Some research has shown increased incidences of atrial fibrillation to be associated but this relationship is not yet clearly established.

Since the valve does not open properly in aortic stenosis, there is a decrease in the forward movement of blood into the aorta. Fetal aortic stenosis impairs left ventricular development, which can lead to hypoplastic left heart syndrome. If untreated, HLHS is lethal, as a result of the inability of the left heart to pump enough blood to sustain normal organ function. In fetal life, this is condition is manageable because the ductus arteriosus acts as a bypass, and supports the delivery of oxygenated blood to the systemic circulation. However, the ductus arteriosus closes during the first few days of life, resulting in systemic circulation failure in babies born with aortic valve stenosis.

Significant mitral valve regurgitation has a prevalence of approximately 2% of the population, affecting males and females equally. It is one of the two most common valvular heart diseases in the elderly.

Fetal aortic stenosis is a disorder that occurs when the fetus’ aortic valve does not fully open during development. The aortic valve is a one way valve that is located between the left ventricle and the aorta, keeping blood from leaking back into the ventricle. It has three leaflets that separate when the ventricle contracts to allow blood to move from the ventricle to the aorta. These leaflets come together when the ventricle relaxes.

There is no exact mechanism for Lutembacher's syndrome but instead a combination of disorders as the result of Atrial septal defect (ASD) and/or Mitral valve stenosis.

Lutembacher is caused indirectly as the result of heart damage or disorders and not something that is necessarily infectious. Lutembacher's syndrome is caused by either birth defects where the heart fails to close all holes in the walls between the atria or from an episode of rheumatic fever where damage is done to the heart valves such as the mitral valve and resultant in an opening of heart wall between atria. With Lutembacher's syndrome, a fetus or infant is usually seen to have a hole in their heart wall (interatrial) separating their right and left atria. Normally during fetal development, blood bypasses the lungs and is oxygenated from the placenta. Blood passes from the umbilical cord and flows into the left atrium through an opening called the foramen ovale; the formaen ovale is a hole between the two atria. Once a baby is born and the lungs begin to fill with air and the blood flow of the heart changes, a tissue flap (somewhat like a trap door) called the septum primium closes the foramen ovale or hole between the two atria and becomes part of the atrial wall. The failure of the hole between the two atria to close after birth leads to a disorder called ASD primium. The most common problems with an opening found in the heart with Lutembacher's syndrome is Ostium Secundum. Ostium Secundum is a hole that is found within the flap of tissue (septum primium) that will eventually close the hole between the two atria after birth. With either type of ASD, ASD will usually cause the blood flow from the right atrium to skip going to the right ventricle and instead flow to the left atrium. If mitral stenosis (the hardening of flap of tissue known as a valve which opens and closes between the left atrium and ventricle to control blood flow) is also present, blood will flow into the right atrium through the hole between the atria wall instead of flowing into the left ventricle and systemic circulation. Eventually this leads to other problems such as the right ventricle failing and a reduced blood flow to the left ventricle.

In addition to the ASD, acquired MS can be present either from an episode of rheumatic fever (the mother has or had rheumatic fever during the pregnancy) or the child being born with the disorder (congenital MS). With the combination of both ASD and MS, the heart can be under severe strain as it tries to move blood throughout the heart and lungs.

A left ventricular outflow tract obstruction (LVOTO) may be due to a defect in the aortic valve, or a defect located at the subvalvar or supravalvar level.

- Aortic valve stenosis

- Supravalvar aortic stenosis

- Coarctation of the aorta

- Hypoplastic left heart syndrome

VSDs are the most common congenital cardiac abnormalities. They are found in 30-60% of all newborns with a congenital heart defect, or about 2-6 per 1000 births. During heart formation, when the heart begins life as a hollow tube, it begins to partition, forming septa. If this does not occur properly it can lead to an opening being left within the ventricular septum. It is debatable whether all those defects are true heart defects, or if some of them are normal phenomena, since most of the trabecular VSDs close spontaneously. Prospective studies give a prevalence of 2-5 per 100 births of trabecular VSDs that close shortly after birth in 80-90% of the cases.

Heart valve dysplasia is a congenital heart defect which affects the aortic, pulmonary, mitral, and tricuspid heart valves. Dysplasia of the mitral and tricuspid valves can cause leakage of blood or stenosis.

Dysplasia of the mitral and tricuspid valves - also known as the atrioventricular (AV) valves - can appear as thickened, shortened, or notched valves. The chordae tendinae can be fused or thickened. The papillary muscles can be enlarged or atrophied. The cause is unknown, but genetics play a large role. Dogs and cats with tricuspid valve dysplasia often also have an open foramen ovale, an atrial septal defect, or inflammation of the right atrial epicardium. In dogs, tricuspid valve dysplasia can be similar to Ebstein's anomaly in humans.

Mitral valve stenosis is one of the most common congenital heart defects in cats. In dogs, it is most commonly found in Great Danes, German Shepherd Dogs, Bull Terriers, Golden Retrievers, Newfoundlands, and Mastiffs. Tricuspid valve dysplasia is most common in the Old English Sheepdog, German Shepherd Dog, Weimaraner, Labrador Retriever, Great Pyrenees, and sometimes the Papillon. It is inherited in the Labrador Retriever.

The disease and symptoms are similar to progression of acquired valve disease in older dogs. Valve leakage leads to heart enlargement, arrhythmias, and congestive heart failure. Heart valve dysplasia can be tolerated for years or progress to heart failure in the first year of life. Diagnosis is with an echocardiogram. The prognosis is poor with significant heart enlargement.